Stabilized distillate fuel oils and additive compositions therefor



United States Patent 3,490,882 STABILIZED DISTILLATE FUEL OILS ANDADDITIVE COMPOSITIONS THEREFOR William P. Dunworth, Wilmington, Del.,assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., acorporation of Delaware No Drawing. Continuation-impart of applicationSer. N 0. 178,536, Mar. 9, 1962. This application Aug. 11, 1966, Ser.No. 571,716

Int. Cl. C101 1/18, 1/22 U.S. Cl. 44-73 9 Claims ABSTRACT OF THEDISCLOSURE Stabilized petroleum distillate fuel oils containing aneffective amount of N,N-dimethylcyclohexylamine and, optionally, an N,N'di(ortho hydroxyarylidene) 1,2- alkylenediamine, for example,N,N-disalicylidene-1,2-propylenediamine.

CROSS REFERENCE TO RELATED APPLICATIONS This is a continuation-in-partof my copending applications Ser. No. 178,536, filed Mar. 9, 1962, nowU.S. Patent 3,186,810, and Ser. No. 291,360, filed June 28, 1963, nowabandoned.

This invention relates to stabilized petroleum distillate fuel oils andto additive compositions for stabilizing such fuel oils. Moreparticularly, the invention is concerned with fuel oils, such as dieselengine fuels and burner oils, that are normally susceptible todeterioration with the formation of insoluble sludge and sedimentespecially at elevated temperatures, which fuel oils have beenstabilized to inhibit such deterioration; and to homogeneous liquidconcentrates of a combination of additive compounds for so stabilizingsuch fuel oils, which concentrates are readily soluble in the fuel oilsand which are unusually effective to so stabilize such fuel oils.

Resistance to discoloration and formation of insoluble matter is adesirable property in present day fuel oils, including heating oils,diesel fuels and gas turbine fuels, particularly when such fuel oils aresubjected to elevated temperatures and oxidizing atmospheres in storageand in use.

Heretofore, a wide variety of additives, including diverse amines, havebeen suggested as stabilizers for distillate fuel oils. For example,Bonner, in U.S. Patent 2,672,408, discloses oil-soluble amines(including N,N- diethylcyclohexylamine) to be effective to retard colorformation in blended oils. In contrast, however, Andress, in U.S. Patent2,945,749, discloses that, while certain tertiary alkyl primary aminesare highly effective in fuel oils to increase color stability and toinhibit sediment formation, during storage, the straight-chained andcycloaliphatic amines not only show no substantial inhibiting effectwith respect to formation of sludge sediment, but they actually show anadverse effect in several instances.

An object of this invention is to improve the stability of petroleumdistillate fuel oils against deterioration such as the formation ofinsoluble sludge, sediment, gum and colored bodies. A specific object isto provide new distillate fuel oil compositions with improved resistanceto the formation of colored and insoluble substances at hightemperatures and under oxidizing conditions. A further object is toprovide additive compositions for distillate hydrocarbon fuel oils,which additive compositions are homogeneous concentrates of a pluralityof co-additives and which concentrates are easily incorporated into saidfuel oils and are unusually effective to inhibit discoloration and theformation and deposition of insoluble sludge and sediment in such fueloils, particularly at high temperatures. Other objects are to providenew compositions of matter and to advance the art. Still other objectswill appear hereinafter.

The above and other objects may be accomplished in accordance with thisinvention which comprises a distillate hydrocarbon fuel oil containing(a) from about 0.00033% to about 0.05% by weight based on the fuel oilof N,N-dimethylcyclohexylamine;

and an additive composition for distillate hydrocarbon fuel oils, whichadditive composition comprises (a) from about to about 97 parts byweight of N,N-

dimethylcyclohexylamine, and

(b) from about 15 to about 3 parts by weight of an N,N' di (orthohydroxyarylidene) 1,2 alkylenediamine metal deactivator in which thearylidene radical contains 6-7 carbon atoms and the alkylene radicalcontains 2-3 carbon atoms.

This invention is based on the discovery thatN,N-dimethylcyclohexylamine is unusually effective to stabilize fueloils against deterioration, particularly at elevated temperatures andunder oxidizing conditions. The novel fuel compositions showsignificantly less insoluble residue formation and better colorstability than untreated fuels. It is believed that the high degree ofstabilization imparted to fuel oils may be attributed to the apparentfact that the N,N-dimethylcyclohexylamine is a uniquely potentantioxidant in these complex hydrocarbon systems at elevatedtemperatures. In contrast, other amines heretofore suggested in the art,including the corresponding N,N-diethylcyclohexylamine, are much lesseffective alone for inhibiting oxidative degradation in petroleumdistillate fuel oils. Unlike many fuel oil additives proposedheretofore, the N,N-dimethylcyclohexylamine is highly resistant toextraction from the fuel by water, and has no adverse affect on fuelproperties in contact with water.

N,N-dimethylcyclohexylamine is well known and conveniently is obtainedby methylating aniline with methanol in the presence of an acidcatalyst, as described in the art (Kirk-Othmer, Encyclopedia of ChemicalTechnology, Interscience, vol. 1, pages 915, 916, 923, 924), andcatalytically hydrogenating the N-methylated aniline product to thecorresponding cyclohexylamine derivative. The technical product, whichmay often contain small proportions, e.g. 15% weight, of theN-monomethylcyclohexylamine, is also suitable for use according to thisinvention. Such product, as well as the pure dimethyl compound, will bereferred to hereinafter as N,N-dimethylcyclohexylamine (DMCHA).

N,N-dimethylcyclohexylamine is normally liquid and readily soluble inthe fuel oils. It is substantially not extractable from the fuel oils byWater, does not contribute to water hazing or emulsification, and isashless. Also, it is compatible with other additives normally associatedwith the finished fuels, such as sludge dispersants, corrosioninhibitors and anti-hazing agents, and may be used to advantage with oneor more of such other additives, as more particularly described in mycopending application Ser. No. 178,536. In addition to the additivecombinations of Ser. No. 178,536, a particularly useful combinationaccording to this invention comprises from about 85% to about 97% byweight of DMCHA and about 15% to about 3% by weight of an N,N-di-(ortho-3 hydroxyarylidene) 1,2 alkylenediamine metal deactivator, wherein thearylidene radical contains 6-7 carbon atoms and the alkylene radicalcontains 2-3 carbon atoms, i.e. 1,2-ethylene and 1,2-propylene.Preferred metal deactivators are N,N-disalicylidene-1,2-prpylenediamineand N,N-disalicylidene-1,2-ethylenediamine.

N,N-dimethylcyclohexylamine, and its combinations with the above metaldeactivators, are normally liquid compositions and may be added as suchdirectly to the fuel oil to be stabilized. Or, if desired, the additionagent may be in the form of a blend, say about 20% to about 80% byweight in a normally liquid inert hydrocarbon carrier solvent, such askerosene, xylene or the like, i.e. the carrier solvent will be in anamount to constitute from about 20% to about 80% by weight of thecomposition.

The quantity of N,N-dimethylcyclohexylamine employed in practicing thisinvention will vary depending on the initial condition and degree ofinstability of the oil, and the elfect desired. While theN,N-dimethylcyclohexylamine may be used in the proportion of about 1 lb.to about 150 lbs. per 1000 barrels of fuel oil (about 0.00033% to about0.05% by weight based on the fuel), normally from about 1 lb./1000 bbls.(0.00033% 'wt.) to about 30 lbs/1000 bbls. (0.01% wt.) are used.

Broadly, the distillate fuel oils are mixtures of hydrocarbons boilingin the range of from about 300 F. to about 900 F., which mixtures arenormally susceptible to deterioration with the formation of coloredbodies and insoluble sludge and sediment under thermal and oxidativeconditions. The present invention is particularly concerned withstabilizing such products as diesel engine oils for stationary, marine,automotive and locomotive type engines, said fuels being particularlydescribed by ASTM specification D-975-53T; and domestic and industrialheating oils, as described in ASTM specification D-396- 48T. Includedare straight run fuel oils, thermally cracked, catalytically cracked,thermally reformed, and catalytically reformed stocks, and blendsthereof as known and commonly employed in the art.

In order to more clearly illustrate this invention, preferred modes ofpracticing it, and the advantageous results to be obtained thereby, thefollowing examples are given in which the amounts and proportions are byweighteX- cept where specifically indicated otherwise.

Example 1 N,N-dimethylcyclohexylamine (DMCHA) andN,N-diethylcyclohexylamine (DECHA) are added, in concentrations of 2.5and 5 lbs. per 1000 barrels, to a typical unstable mid-continentdistillate hydrocarbon oil (designated Fuel A), the additions being madeto the freshly produced fuel at the refinery. At a second mid-continentrefinery, these amines are added at the same concentrations to a blendcontaining by volume 65% catalytic cracked light cycle oil and 35%straight run No. 1 burner oil (designated Fuel B).

The effectiveness of the amine to inhibit deterioration at elevatedtemperatures is illustrated by the 300' F. Accelerated Fuel OilStability Test (also sometimes referred to as the EMD Diesel Fuel Test,the Union Pacific Test, or the Nalco Test). This test is designed todetermine the relative stability of distillate fuels under shortterm,high temperature, aging conditions involving air exposure. It is alsoused to evaluate the eflfectiveness of additives in inhibiting residueformation and color degradation of distillate fuels under the conditionsof the test. The proceure consists of aging the fuel sample at 300 F.for 90 minutes, cooling to room temperature, and.

collecting any insoluble residue by vacuum filtration through a filterpaper (blotter). The resultant blotter is compared with a set ofstandards to obtain a numerical rating of 1 to for the performance ofthe fuel. The amount and color of the precipitate collected on theblotter determines the rating and indicates the extent of fueldeterioration. The lower the rating the more stable the fuel. Ingeneral, a rating of 7 or less is desirable, and 7 may be regarded asthe dividing line for purposes of assigning a pass (7 or less) or fail(greater than 7) rating to the fuel under test. Table 1 compares theeflectiveness of these two amines in preventing deterioration at hightemperatures as determined by this test.

In addition to the blotter rating, the ASTM color (accoring to ASTMdesignation: D-1500-58T) of the fuel is also determined before and afteraging. Typical results obtained with DMCHA are given in Table 1,together with, for comparison, results for DECHA as additive.

TABLE l.-N,N-DIMETHYLCYCLOHEXYLAMINE (DMCHA) ANDN,N-DIETHYLCYOLOHEXYLAMINE (DECHA) [Compared in the 300 F. AcceleratedFuel Oil Stability Test] The above results show thatdimethylcyclohexylamine is clearly superior to the prior artdiethylcyclohexylamine for stabilizing distillate hydrocarbon oilsagainst deterioration at high temperatures.

Example 2 The effectiveness of DMCHA to inhibit sediment and colorformation in five diiferent typical No. 2 fuel oils (A, B, C, G and I)under oxidizing conditions is further illustrated by means of stillother methods of evaluation, as described below.

(A) Proposed ASTM Accelerated Stability Test for Distillate Fuel Oil(Appendix 16, 1961 ASTM Standard on Petroleum Products).

The fuel oil under test is aged at 203 F. for 16 hours while oxygen isbubbled through the sample, which is then filtered to remove theinsolubles, the amounts of the insolubles determined, and the color ofthe filtrate measured. Results on fuel oils A, B and C are shown inTable 2-A and are expressed in terms of total insolubles and degree ofdiscoloration produced in the filtered oil under these conditions.

TABLE 2A.-STABILIZATION OF FUEL OIL AGAINST OX- IDATIVE DETERIO RATIONIN PROPOSED ASTM ACCEL- ERATED STABILITY TEST for No. 2 Fuel Oils.

Samples of the fuel oil are aged 16 hours at 212 F. under p.s.i.g.oxygen in a bomb, then cooled, filtered and the soluble-, insoluble-,and total gum determined. The color of the filtrate is also measured.Two typical No. 2 fuel oils (I and G) were so tested, with and without'N,N-dimethylcyclohexylamine (DMCHA) and with both DMCHA and the metaldeactivator, N,N'-disalicylidene- 1,2-propylenediamine (DMD). Theresults are shown in Table 2-B.

TABLE 2-B.--RETARDING GUM FORMA- IN THE GREAT LAKES PIPELINE AdditiveCone. lbs/1000 bbls. of

No. 2 Fuel Oil Gum, lug/100 ml. 1

0 or DMCHA DMD Sol. Insol. Total ASTM Samples of a typical commercialNo. 2 fuel oil, with and without DMCHA (7.5 -lbs./ 1000 bbls.), werevigorously shaken for minutes with 10% by volume of tap water. Thesamples, before and after this water extraction, were evaluated in the300 F. Accelerated Fuel Oil Stability Test described in Example 1. Fueloil without DMCHA showed a blotter rating of 17 before and 16 afterwashing, and ASTM color of L 8.0 and 7.0 before and after washing. Fueloil containing 7.5 lbs/1000 bbls. of DMCHA showed the same blotterrating of 1 before and after washing, and the same ASTM color rating ofL 1.5 before and after washing.

A series of No. 2 fuel oils were treated to contain 20 lbs/1000. bbls.of DMCHA and tested for emulsification and haze tendencies as follows:

6 Under these conditions, the treated and untreated fuels showedsubstantially identical performance in their rates of recovery tosubstantially complete light transmission.

Example 4 A commercial No. 2 fuel oil was treated to containN,N-dimethylcyclohexylamine (DMCHA) or Primene 81R (an amine additiveunderstood to consist essentially of C -C tertiary alkyl primary aminesas disclosed by Andress in US. Patent 2,945,749) for purposes ofcomparison in the quantities tabulated below. The resulting blends weretested for high temperature stability according to the Accelerated FuelOil Stability Test described in Example 1. The results are shown inTable 3.

TABLE 3 Condition of Blotter Appearance and Rating Primene 81R DMCHAAdditive conc., lbs/1,000 bbls.:

None Black, 18 Black, 18. 1. do. Grey black, 16. 2. Black, 17 Grey, 11.3 Grey black, 16...- Light grey, 8. 5. do Tan, 5. 7 Dark grey, 15....-Tan. 4, 10 Med. grey, 14. D

0. Light tan, 3.

The data show that the cycloaliphatic tertiary amine is clearly superiorto the branched chain alkyl primary amine as high temperaturestabilizer.

Example 5 N,N-dimethylcyclohexylamine (DMCHA) or other amine asidentified below in Table 4 was blended by stirring into a commercialNo. 2 fuel oil to provide a concentration of 10 lbs. of amine per 1000bbls. of oil. The effectiveness of the various amines to inhibitdeterioration and insoluble residue formation at elevated temperaturesis illustrated by the 210 F. Enjay Test and by the 300 F. AcceleratedFuel Oil Stability Test described in Example 1. The Enjay Test involvesa 16 hour exposure of the oil sample at 210 F. and is more fullydescribed by Geller et al. in US. Patent 2,912,314 (Example 1) and byErtelt et al. in U.S. Patent 2,974,025 (Example 2). The results of thesetests are shown in Table 4.

TABLE 4.COMPARISON OF DMCHA WITH OTHER AMINES IN FUEL OIL 1 N-Me standsfor N -monomethyl and N ,N-Me stands for N,N-dimethyl.

In the emulsification test, the oil is agitated violently with 5 volumepercent water for 5 minutes in a high speed mixer. If, after standingfor 24 hours, no emulsion remains, the procedure is repeated using thesame water and fresh oil sample. The number of oil changes that can bemade without creating an emulsion is taken as the criterion ofperformance.

Under these conditions, the fuel oils, with and Without DMCHA, performedidentically.

In the haze test, the fuel oil plus 0.2 volume percent water is agitatedin a high speed mixer for 5 minutes, and the amount of haze produced isdetermined periodically by withdrawing samples for light transmissionmeasurements.

The data show that DMCHA and N-monomethylcyclohexylamine are highlyeffective to stabilize fuel oil under the conditions of both tests,whereas Primene 81R is satisfactorily effective only under the the lessstringent thermal conditions of the Enjay test. Further, theeffectiveness at the higher temperatures appears attributable to theN-methyl substituents in the mono-and dimethylcyclohexylamines since theparent cyclohexylamine is virtually ineffective in the 300 F. test. Thiseffect of the N-methyl substituents appears to be peculiar to thecyclohexylamine system, since it is absent in the corresponding anilineswherein the N-methyl substituents show the opposite effect of decreasingor destroying the effectiveness of aniline for these purposes.

Example 6 Dimethylcyclohexylamine (DMCHA) and diethylcyclohexylamine(DECHA) are added in equal concentrations to samples of a catalyticcracked light cycle oil, having an API gravity of 60 F. of 28.3 and anASTM distillation range of 415 to 632 F. immediately as it is producedat a refinery. The treated samples are then blended with straight runNo. 1 burner oil having an API gravity at 60 F. of 42.5 and an ASTMdistillation range of 345 to 540 P. so as to provide a fuel oilcontaining 65% cycle oil and 35% burner oil having an API gravity of 60F. of 33.1 and an ASTM distillation range of 360 to 616 F. The resultingfuels are tested in the 300 F. stability test described in Example 1 andalso in the Great Lakes Pipeline Test described in Example 2. Table 5shows the results.

3. A distillate hydrocarbon fuel oil of claim 1 which also contains fromabout 3% to about by weight, based on the N,N-dimethylcyclohexylamine,of an N,N'- di(ortho hydroxyarylidene) 1,2 alkylenediamine in which thearylidene radical contains 6-7 carbon atoms and the alkylene radicalcontains 2-3 carbon atoms.

4. A distillate hydrocarbon fuel oil of claim 2 which also contains fromabout 3% to about 15% by weight, based on theN,N'-dimethylcyclohexylamine, of an N,N- di(ortho hydroxyarylidene) 1,2alkylenediamine in which the arylidene radical contains 6-7 carbon atomsand the alkylene radical contains 2-3 carbon atoms.

5. A distillate hydrocarbon fuel oil of claim 4 in which the N,Ndi(ortho hydroxyarylidene) 1,2 alkylenediamine is N,N disalicylidene 1,2propylenediamine.

6. An additive composition for distillate hydrocarbon fuel oils, whichcomprises TABLE 5.DMCHA COMPARED WITH DECHA AS FUEL QIL STABILIZER GreatLakes Pipeline Test Concen- 300 F., Stability Test tration Decrease inGum lbs./ Gum, ing/100 m1. Formed, percent 1,000 ASTM Blotter ASTM bblscolor rating color S01. Insol. Total Sol. Insol. Total iiiiii 0.0 D s 18L 6.0 31.2 17.2 48.4 DMOHA 6.0 L 2.5 3 L 4.0 12.6 4.2 16.8 60 76 65DECHA 6.0 L 3.5 11 L 5.5 31.4 12.1 43.5 -1 10 It will be understood thatthe preceding examples have (a) from about 85 to about 97 parts byweight of N,N- been given for illustrati e purposes solely and that this30 dimethylcyclohexylamine, and invention is not limited to the specificembodiments de- (b) from about 15 to about 3 parts by weight of anscribed therein. On the other hand, it will be apparent N',N' d1 (orthohydroxyarylidene)-1,2 alkyleneto those skilled in the art that, subjectto the limitations dlamlne m which the arylldene radical contains 6-7set forth in the general disclosure, many variations and carbon atomsand the alkylene radlcfll 6011131118 modifications can be made in thematerials, proportions carbon atoms.

and conditions employed, without departing from the spirit or scope ofthis invention.

From the preceding description, it will be apparent that this inventionprovides distillate hydrocarbon fuel oils which are stabilized againstobjectionable deterioration by N,N-dimethylcyclohexylamine and by novelcombinations of additives which are unusually effective for suchpurpose. It will also be apparent that this invention provides noveladditive compositions for distillate hydrocarbon fuel oils whichcompositions are homogeneous concentrates of combination of co-additiveswhich are unusually effective for stabilizing distillate hydrocarbonfuel oils. Accordingly, it will be apparent that this inventionconstitutes a valuable contribution to and advance in the art.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A distillate hydrocarbon fuel oil containing from about 0.00033% toabout 0.05% by weight, based on the fuel oil, ofN,N-dimethylcyclohexylamine.

2. A distillate hydrocarbon fuel oil of claim 1 containing from about0.00033% to about 0.01% by weight, based on the fuel oil, ofN,N-dimethylcyclohexylamine.

7. An additive composition of claim 6 which also contains a normallyliquid inert hydrocarbon carrier solvent in an amount to constitute fromabout 20% to about by weight of the composition.

8. An additive composition of claim 6 in which the N,N' di(orthohydroxyarylidene) 1,2 alkylene diamine is N,N' disalicylidene 1,2propylenediamine.

9. An additive composition of claim 8 which also contains a normallyliquid inert hydrocarbon carrier solvent in an amount to constitute fromabout 20% to about 80% by weight of the composition.

References Cited UNITED STATES PATENTS 2,284,267 5/1942 Downing et a1.44-73 FOREIGN PATENTS 528,564 7/1956 Canada.

DANIEL E. WYMAN, Primary Examiner MRS. Y. H. SMITH, Assistant ExaminerUS. Cl. X.R. 44-72 Disclaimer 3,490,882.-William P. D mworth,\Vilmington, Del. STABILIZED DISTIL- LATE FUEL OILS AND ADDITIVECOMPOSITIONS THERE- FOR. Patent dated J an. 20, 1970. Disclaimer filedSept. 17, 197 6, by the assignee, E. I. du Pont de N emours and Company.The term of this patent subsequent to June 1, 1982, has been disclaimed.

[Oyfioial Gazette November 3, 1976.]

